4.6.1 Forces Flashcards
What is the difference between scalar and vector quantities?
scalar quantities just have a magnitude (a number)
Vector quantities have a magnitude and a direction
i.e. 10 miles is a scalar quantity
10 miles North would be vector
Is Force a scalar or vector quantity?
Vector - as forces act in a certain direction
How can we represent a vector with a diagram?
Use an arrow. The size of the arrow shows the magnitude - the direction shows the direction!
What is the difference between a contact and non contact force?
In contact forces the objects must be physically touching i.e. friction between the road and a tyre.
Non contact forces the objects can be physically separated i.e. a magnet is attracted to another magnet even though it is not touching.
Give some examples of contact forces.
Friction, air resistance, tension, normal contact force (upthrust)
Give some examples of non contact forces
magnetism, gravity, electrostatic forces
What is the equation for work done?
What unit does each part need to be in?
Work done = distance x force
Work done in Joules (J)
Distance in metres (m)
Force in Newtons (N)
What is the definition of a ‘joule’ of energy.
A joule is 1 newton metre. This is because one joule of energy is used when a force of 1N moves an object by 1 metre.
What is the difference between weight and mass?
Mass depends on how many atoms something is made of.
Weight is the force acting on an object due to gravity.
What is the equation to find weight?
Weight (N) = Mass (kg) x gravitational field strength (N/kg)
What is the relationship between mass and weight?
It is directly proportional. If mass doubles, then so does weight.
Would your mass be different on the moon?
Would your weight be different on the moon?
Explain your answer.
Your mass would be the same as the amount of atoms you are made up of does not change.
Your weight would change. It would be less on the moon as the gravitational field strength is weaker.
How can we measure weight?
Using a newton meter. This measures weight in Newtons.
How can an object gain gravitational potential energy?
Raise it up above the ground. The higher your raise it the more potential it has.
What is the equation to calculate gravitational potential energy?
GPE (J) = mass (kg) x gravitational field strength (N/kg) x height raised (m)
What does it mean if an object has been ‘elastically deformed’?
If you stretch an object, like an elastic band, and it returns to its original shape it has been elastically deformed.
What does it mean if an object has been ‘inelastically deformed’?
If you stretch an object, like plastercine, and it does not return to its original shape it has been inelastically deformed.
What happens when you apply a force to a spring?
It stretches. The relationship between the force (weight) and the extension of the spring (how stretched it is) is directly proportional. As the force doubles the extension of the spring also doubles.
What is the equation linked force and extension?
Force (N) = spring constant (N/m) x extension (m)
How do you convert from cm to m?
How many metres are in 200cm?
divide by 100
2m
How do you convert from km to m?
How many metres are in 0.5km?
multiple by 1000
500m
What is the ‘limit of proportionality’?
This is the maximum amount of force that a spring/elastic band can take and stretch in an elastic way. Past the limit of proportionality there will not be a link between the force applied to the spring and the extension.
What type of energy is stored in a compressed spring or a stretched elastic band?
Elastic potential energy
What is the equation to calculate elastic potential energy?
elastic potential energy (J) = 0.5 x spring constant (N/m) x extension(m)squared
Why do we need a spring constant in calculations?
All springs are different and need a different amount of force to stretch them.
